Abstract

Although the carbon nanotube(CNT) features superior thermal properties in its pristine form, the chemical functionalization often required for many applications of CNT inevitably degrades the structural integrity and affects the transport of energy carriers. In this article, the effect of the side wall functionalization on the phonon energy transmission along the symmetry axis of CNT is studied using the phononwave packet method. Three different functional groups are studied: methyl (–CH3), vinyl (–C2H3), and carboxyl (–COOH). We find that, near Γ point of the Brillouin zone, acoustic phonons show ideal transmission, while the transmission of the optical phonons is strongly suppressed. A positive correlation between the energy transmission coefficient and the phonon group velocity is observed for both acoustic and optical phonon modes. On comparing the transmission due to functional groups with equivalent point mass defects on CNT, we find that the chemistry of the functional group, rather than its molecular mass, has a dominant role in determining phonon scattering, hence the transmission, at the defect sites.

This article is benefited from the insightful discussions with Professor Simon Phillpot and Professor Tim Fisher. Authors are grateful to Dr. Byung-Lip (Les) Lee and (U.S.) Air Force Office of Scientific Research (USAFOSR) for the financial support. Authors also thank the Air Force Research Laboratory DoD Supercomputing Resource Center for the computational resources provided.

Article outline:I. INTRODUCTIONII. METHODIII. RESULTS AND DISCUSSIONA. General characteristics of the energy transmissionB. Specifics depending on the functional groupIV. SUMMARY